The present invention relates to electromechanical apparatus which commonly is called an automatic program controller, repeat cycle timer and time sequence controller or programmer. Apparatus of this type is well known and is comprised of a plurality of cams or drums mounted on a common axle which is rotated by a synchronous motor. An electrical switch is mounted in proximity to each cam or drum and each switch controls an independent circuit, or respective subcircuit of a system. Typically, the cams or drums are independently adjustable in order that the ON and OFF times of the respective switches may be independently programmable as a function of the physical adjustment of a camming surface or the placement of switch actuator means on the individual rotatable cam or drum.
Apparatus of this type has found wide and diverse use in industry and it is desirable that it be constructed in such a way as to be readily adaptable to the diverse applications to which it may be put. For example, the number of independent circuits or subcircuits to be controlled may vary considerably with different users, and the number of required circuits may change from time to time with one user. Additionally, the power requirements of the various circuits to be controlled may be different so that switches of different power handling capabilities may be required in one time sequence controller. Furthermore, for the apparatus to be of optimum flexibility and utility, it is desirable that switches and switch actuator means be easily added, replaced and removed from the apparatus with a minimum of effort and with a minimum investment in component parts. Commonality of parts thus is an important factor in minimizing cost and effort.
Past attempts to overcome some of the deficiencies and to achieve some of the advantages mentioned above have resulted in modular construction of time sequence controllers. In this type of construction the switch and switch actuating means such as a cam or drum assembly are manufactured in such a way that one switch and one actuator means may be assembled as a modular unit and then a plurality of modules assembled together to comprise a completed multiswitch controller assembly. U.S. Pat. Nos. 3,470,335, 3,569,992 and 3,678,225 are representative of past efforts. However, some of the apparatus shown in the mentioned patents is rather complicated and expensive to manufacture, and other apparatus does not have the desired degree of flexibility and commonality of modular parts. One deficiency in the known prior art is that the assembled modules are held together by a common fastening means such as a long tie rod that passes through all the modules and is bolted to end plates at opposite ends of the assembled modules. To add or remove modules, the common tie rod must be withdrawn and replaced by one of a different length. This requires that a number of tie rods of different lengths must be maintained in stock to afford flexibility in the number of modules that may be assembled. When a tie rod is withdrawn to add or remove modules, or when the bolts of the tie rod are loosened to allow replacement of an independently housed switch, the switches and possibly other parts of the assembly may become displaced or misaligned, thus adding to the complexity of reassembling the modules.
The apparatus of the present invention overcomes the above problems by providing relatively simple and economically manufactured component parts having a very high degree of commonality. Additionally, modules may be added, removed and changed with a minimum of effort and without appreciably affecting other modules of the assembly.